The invention described herein was made in the course of, or under, Contract AT(29-1)-1183, with the United States Energy Research and Development Administration (formerly the United States Atomic Energy Commission).
This invention relates to the growth of mercuric iodide crystals, and more particularly to a process for purification of mercuric iodide to be utilized as a source material for the growth of such crystals.
Since the advent of semiconductor detectors, efforts have been directed to the development of detector materials having a sufficiently high atomic number so as to overcome the low photoelectric efficiency that results from low atomic number detector materials. Compounds such as CdTe and, more recently, HgI.sub.2 have been explored. While mercuric iodide (HgI.sub.2) promises to be one of the most potentially useful, high atomic number, room temperature operable radiation detector materials structural imperfections due primarily to high impurity concentrations have led to problems of carrier trapping and detrapping and of detector fabrication. While substantial effort has been directed to methods for growing HgI.sub.2 crystals, relatively little effort has been directed to the development of high purity HgI.sub.2 raw material to be used for growth of detector quality HgI.sub.2 crystals. Technical literature directed to purification of the HgI.sub.2 raw material is exemplified by an article by S. P. Swierkowski, et al. Appl, Phys, Ltrs. 23, 281, 1973, and an article by M. Schieber, et al, Journal of Crystal Growth 24/25. 205-211, 1974. As noted in the Journal of Crystal Growth article, in establishing the detector quality of a given crystal, experiments indicate that purity is a more critical requirement than physical perfection, and a higher degree of purification of both solvent and raw materials would lead to high quality detector crystals.